George Carlin died in June of heart failure at age 71. ((HBO/Associated Press))

The late comedian George Carlin, immortalized in his Seven Words You Can Never Say On TV routine, was honoured with the Mark Twain Prize for American Humor, the only trophy that the counterculture performer saw as a legitimate comedy prize.

A cavalcade of comedians, including Lily Tomlin, Joan Rivers and Jon Stewart, paid tribute to Carlin — who died in June — at the John F. Kennedy Center for the Performing Arts in Washington, D.C., Monday night.

"For all his anti-establishment cred, he was a working man," Stewart said on stage.

"He punched in. He sat down and he wrote. He respected what he did."

Fellow comedians hailed the maverick performer for pushing the boundaries of free speech, especially with his Seven Words routine. It was the subject of a U.S. Supreme Court ruling on free speech that upheld the government's right to sanction broadcasters who air offensive language while children might be listening.

"That was when I realized you could make money for saying things my dad used to say when he was fixing the car," said Dennis Leary.

The prize was announced shortly before Carlin died of heart failure in June at the age of 71.  It marks the first time in the award's 11-year history that it has been presented posthumously.

"I think he represented a lot of what Mark Twain did for our country, not only being smart and funny but also being a sharp commentator," said the comedian's daughter, Kelly Carlin McCall.

In Carlin's 50-year career, he recorded 23 comedy albums, won four Grammys and made more than a dozen TV specials. Carlin's final TV special for HBO, It's Bad For Ya, is scheduled for release on DVD on Nov. 25.

McCall said her father left behind an uncompleted autobiography. It is scheduled to be published next year with herself, Carlin's brother, Patrick, and others filling in the gaps.

With files from the Associated Press